// FUME EXTRACTION SILENCING
In many industrial environments the issue noise/sound pollution is very important, constant sound above 85 decibels is enough to cause damage to a person hearing. HSE covers noise levels in the workplace and can be viewed here.
With lasers becoming far more common in a wider market there has been considerable development in the need for quieter running systems. In areas where the ambient noise is low, a fume extractor running at 85 db is fairly disturbing, in fact within a classroom environment or in clean rooms it is certainly more than a nuisance.
The simplest form of silencing is acoustic lagging of the fume extraction unit, coupled with rubber mounts or wheels which reduce the vibration transfer to the environment. Most manufacturers incorporate this as a standard. However to truly silence the vacuum noise a silencing component needs to be used at the intake and discharge ends.
These come in 2 main types (designs vary depending on manufacturer):
1. // REACTIVE
The reactive silencer utilizes a series of expansion chambers that reduces the air flow speed prior to being forced through a series of dis-continuities which disrupt and reflect the sound back from its source. This is particular effective in laser fume systems which work on a slower motor speed. They can contribute to a loss of noise by up to 40 decibels. And if used in conjunction with the absorptive type silencer at either end this can increase upto 40% more.
2. // DIFFUSER / ABSORPTIVE
This method is fairly simple in its application. Used primarily where pressures are low, sound waves travel through silencer and are baffled by the acoustically packed section, it absorbs all the vibration and sound energy so that when the noise is discharged it is between 10 -35 decibels quieter. With this in mind various companies have developed their own silencing devices for fume extraction units. Purex for example have the 'whisper stream' technology which is essentially a reactive device built within the unit. This claims a decibel level of 45 DB equates roughly to the same as a noisy conversation.
To see how loud other activities are visit here.
